Spectroscopic ellipsometry (SE) is a powerful technique for determining a wide variety of optical and physical properties of materials. The full spectra of the ellipsometric parameters Δ and Ψ as a function of wavelength from the ultraviolet region (UV) (wavelengths in the range of between about 10 nm and about 400 nm) to the infra-red region (IR) (wavelengths in the range of about 700 nm to about 300 μm) can be determined with a high degree of precision and accuracy in a few seconds. In practice, most commercial SE systems collect data between about 140 nm and about 2000 nm. Such data can also be processed to provide (i) the values of the dielectric functions (i.e. the real and the imaginary parts of the optical dielectric constant as a function of wavelength) of semiconductors, metals, and wide band gap materials; (ii) depth-profiles of interfaces, thin films, and multilayer structures with almost atomic resolution; (iii) the composition for any layers (bulk, interface, or surface) that are composites or alloys; (iv) the micro-roughness of the surface layer; and (v) the true near-surface temperature of samples in the process chamber when used as an in-situ diagnostic tool. Furthermore, the results discussed above obtained by SE are reliable and trustworthy, with excellent corroboration with independent results of cross-sectional transmission electron microscopy (XTEM), Rutherford backscattering spectrometry (RBS), and atomic force microscopy (AFM) studies on the same multilayer structures. However, the spot size (e.g. the sample area) of spectroscopic ellipsometers is large compared to single wavelength ellipsometers. Additionally, the cost of spectroscopic ellipsometers exceeds that of single wavelength ellipsometers.
It is desirable to develop methods that would allow the refractive index of materials to be determined as a function of wavelength based on single wavelength ellipsometer data.